So what are Percs and Deeps?
Sometimes referred to as Percs and Deeps, these are 2 different tests generally done on the same day.
The First test, the Perc test, is a test of the percolation rate of your soil. A small hole is dug with a post hole digger, and water is poured in. The Installer and town Sanitarian monitor the rate of percolation. They do this by measuring the amount of water in the hole, and during set intervals of 5 , 10, or more minutes, they determine how quickly the water is being absorbed into the soil. The slowest reading determines the official rate. Soil that drains quickly generally receives an “Inch in 5” or “Inch in 10” rating, which just means that 1 inch of water receded in 5 or 10 minutes. So an “Inch in 40” would be a very slow reading, and require some fill to be brought in to the site.
Next, a deep test is performed to learn about the types of soil. This test involves digging through the layers of soil, to find what soils make up your property, and find where the water table is in your area. Using an excavator, an 8 foot hole is dug. A town sanitarian will inspect the cross section of soils, to see if there are any soils which would restrict the water in a septic field from draining into the soil. If a water table is high, signs of water will show up in the dig, and that also is considered a restrictive layer.
Once the Perc and Deep test is complete, a septic system can be designed to properly fit the property and exact location where the system will be built.